The ability to replace or repair diseased heart valves with prosthetic devices has provided surgeons with a method of treating valve deficiencies due to disease and congenital defects. A typical procedure involves the removal of the natural valve and surgical replacement with a mechanical or bioprosthetic valve. Another technique uses an annuloplasty ring to provide structural support to the natural root which supports the natural annulus of the valve.
Studies have shown that structural abnormalities of the heart can render it susceptible to the development of invasive infection of the heart valve called Subacute Bacterial Endocarditis (SBE). The tissue abnormalities can interrupt the blood flow pattern in the heart, generating areas of turbulence and stasis. Transient bacteria can adhere to heart tissues in these areas of abnormal flow and establish an infection (endocarditis). Once endocarditis is established it is extremely difficult to cure. Once the natural valve is damaged by infection, it may need to be replaced. Usually a biological valve is used in these instances for the replacement due to the lower susceptibility of infection.
Following implantation, there is a risk of postoperative systemic infection. Prosthetic Valve Endocarditis (PVE) is an infection that can be associated with a heart valve prosthesis. Heart valves include a fabric sewing cuff or other fabric portion which is used to suture the heart valve to heart tissue. Over time, fibrous tissue grows into the sewing cuff and encapsulates the cuff. Bacteria can colonize in the wound associated with the implant and the fabric of the sewing cuff. Studies have shown that the growth of tissue into the cuff material can attract circulating bacteria or other pathogens. For this reason, heart valve recipients are cautioned regarding activities which may introduce bacteria into their bloodstream, such as dental work.
With respect to replacement heart valves, care must be taken to ensure sterility during production and to prevent contamination during the replacement valve implantation process. For example, to reduce perioperative contamination, some surgeons apply antibiotics prior to implantation. These techniques, however, have relatively short term effectiveness. Others have proposed the use of drug delivery systems designed for antibiotic therapy and these systems are also relatively short-term. In spite of these efforts, PVE occurs in about 2% to 4% of patients.
Other prior art includes U.S. Pat. No. 5,464,438, issued to Menaker. This reference teaches the use of gold metallic coatings on biomedical devices, such as heart valves. This surface treatment is intended to prevent thrombosis.